Many South Island high country stations are leasehold land. Historically farmers leased the land from the Crown. They ran sheep, and seasonally burned tussocklands to encourage new growth. A tenure review process has been under way since the early 1990s. Under this voluntary process, the Crown reviews the conservation value of land under high country leases. Areas of conservation importance (usually at higher altitudes) can be placed under Department of Conservation management. Areas less important for conservation (usually on more fertile river flats and lower hills) are freeholded to farmers.